Determining location of mobile device

ABSTRACT

Embodiments of the present invention relate to a method and apparatus for determining the location of a mobile device. Specifically, the method comprises: receiving the location message from a neighboring mobile device, the location message comprising the location of the neighboring mobile device at the current time which is obtained by the neighboring mobile device through calculation utilizing signals received from satellites; and estimating the location of the mobile device at the current time based on stored locations of the mobile device at historical time, stored locations of the neighboring mobile device at the historical time, and the received location of the neighboring mobile device at the current time.

FIELD OF THE INVENTION

Embodiments of the present invention relate to the field of informationservice; specifically, embodiments of the present invention relate to amethod and apparatus for determining the location of mobile device.

DESCRIPTION OF THE RELATED ART

Currently, a plurality of location-based services (LBS) evolve in theinformation service field. These services are information andentertainment services utilizing the geographical location of mobiledevice. The mobile device (with software and hardware supporting LBS)may access these services via a mobile network so as to be used in aplurality of scenarios. For example, a user of the mobile device mayquery the LBS for the nearest business or service, such as an ATM orrestaurant, locate friend on a map displayed on the mobile device, orreceive warning for traffic jam at a place, etc.

SUMMARY OF THE INVENTION

In the context, objectives of the present invention comprise providing amethod and apparatus for determining the location of a mobile device,where the method and apparatus may reduce energy consumption of themobile device and provide highly accurate location estimation.

Some embodiments according to one aspect of the present inventionprovide a method for determining the location of a mobile device. Forexample, the method may comprise: receiving location message from aneighboring mobile device, the location message comprising the locationof the neighboring mobile device at the current time obtained by theneighboring mobile device through calculation utilizing signals receivedfrom satellites; and estimating the location of the mobile device at thecurrent time based on the stored locations of the mobile device at thehistorical time, the stored location of the neighboring mobile device atthe historical time, and the received location of the neighboring mobiledevice at the current time.

Some embodiments according to another aspect of the present inventionprovide an apparatus for determining the location of a mobile device.For example, the apparatus may comprise: location message receivingmeans configured to receive location message from neighboring mobiledevice, the location message comprising the location of the neighboringmobile device obtained by the neighboring mobile device throughcalculation utilizing signals received from satellites; and locationestimating means configured to estimate the location of the mobiledevice at the current time based on stored locations of the mobiledevice at historical time, a stored location of the neighboring mobiledevice at the historical time, and the received location of theneighboring mobile device at the current time.

The illustrative solutions provided by the illustrative embodiments ofthe present invention at least may have one of the following notabletechnical effects:

1. Energy consumption is reduced because the mobile device does not needto frequently perform satellite signal-based locating process thatrequires high energy consumption.

2. Accuracy of location estimation of the mobile device can beguaranteed because the communication distance supported by short-rangecommunication is rather short (generally less than 10 m).

BRIEF DESCRIPTION OF THE DRAWINGS

Through reading the following detailed description with reference to theaccompanying drawings, the above and other objectives, features andadvantages of the illustrative embodiments of the present invention willbecome more comprehensible. In the drawings, a plurality of embodimentsof the present invention will be illustrated in an illustrative andnon-limiting manner, wherein:

FIG. 1 schematically illustrates an application scenario of illustrativeembodiments of the present invention;

FIG. 2 schematically illustrates a flow chart of a method fordetermining the location of a mobile device according to theillustrative embodiments of the present invention;

FIG. 3 schematically illustrates the time-location sequence stored inthe mobile device according to illustrative embodiments of the presentinvention;

FIG. 4 schematically illustrates a block diagram of an apparatus fordetermining the location of a mobile device according to theillustrative embodiments of the present invention; and

FIG. 5 schematically illustrates a block diagram of a mobile device thatbenefits from the illustrative embodiments of the present invention andthat may be the illustrative apparatus according to the illustrativeembodiments of the present invention.

In the drawings, like or corresponding numerical signs indicate the sameor corresponding parts.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the principle and spirit of the present invention will bedescribed with reference to various illustrative embodiments. It shouldbe understood that these embodiments are provided only to enable thoseskilled in the art to better understand and further implement thepresent invention, not intended for limiting the scope of the presentinvention in any manner.

According to the embodiments of the present invention, a method andapparatus for determining the location of a mobile device is provided.

In this text, it should be understood that each “location” involved is acoordinate pair on a map (for example, a pair of x coordinate and ycoordinate); each displacement or velocity involved is a vector, i.e.,comprising both number and direction; the unit mW involved indicatesmiliwatt, and dBm indicates decibel relative to one milliwatt; andvarious messages involved may, for example, be in a format of variouskinds of short-range communications that already exist (such asBluetooth, WiFi, etc.) or will be developed in future, even in a formatderived from dedicated negotiation between various mobile devices forcommunication. Different message formats and transmission methods haveno limitation on the present invention. Besides, each naming is merelyfor distinguishing and convenience of depiction, which has no anyimplication of limiting.

Hereinafter, the principle and spirit of the present invention will bedescribed in detail with reference to a plurality of representativeembodiments of the present invention.

Main Idea of the Invention

As above mentioned, the location-based service becomes very popular dueto its convenience and entertainment nature. However, the inventors findthat such location-based service (for example, GeoLife, Micro-Blog,TrafficSense and Pothole Patrol) requires the mobile device toperiodically (for example, every 5 seconds) receive signals fromsatellite utilizing its positioning device (for example, GPS module) soas to calculate its current location, which will incur unacceptable highenergy consumption to the mobile device. Such high energy consumptionmay significantly shorten the battery service time of the mobile phone.Thus, user experience of the mobile device will be dampened.

For overcoming the above drawbacks in the prior art, at least two keychallenges must be addressed: first, how to lower the energy consumptionof the locating service; and second, how to guarantee locating accuracy(as is known that the locating accuracy of, for example GPS, is lessthan 10 m).

To this end, the inventors find:

1. The coverage scope of short-range communication, for exampleBluetooth, WiFi, and the like is acceptable. For example, the maximumallowed power of the Bluetooth technology is below 2.5 mV (4 dBm), witha coverage of about 10 m;

2. Its energy consumption is notably lowered compared with for examplethe GPS.

3. In real life, a personal area network (PAN) of the mobile device (forexample, provided by Bluetooth, WiFi, etc.) always has a plurality ofmobile devices that support locating function and short-rangecommunication mechanism;

4. For the sake of saving battery life, users of these mobile deviceswould like to share the location required by a locating service with themobile devices of others; and

5. Energy consumption will be effectively lowered by lowering thefrequency of calculating the location required by locating the service.

In view of the above findings, the inventors provide a method andapparatus for determining the location of a mobile device, with its coreideas being summarized below:

A mobile device among a plurality of mobile devices in a PAN area, afterobtaining an accurate location through calculation utilizing receivedsatellite signals, may share the location with other mobile devices byusing a lower energy-consumption short-range communication mechanism.Therefore, it would be unnecessary for the other mobile devices tocalculate their own locations based on the signal received from thesatellite. Instead, these mobile devices may estimate their ownlocations utilizing the accurate location of the mobile device nearby(for example, within about 10 m), so as to reduce the frequency ofcalculating the location required by locating service utilizing thesignal received from the satellite.

For example, suppose there are 9 similar mobile devices exist in the PANarea of the mobile device M. If the mobile device M needs to calculateits location once every 5 seconds based on the satellite signal in theprior art, then, after the technical solution of the present inventionis applied, it only needs to calculate its location every 50 seconds tothe utmost based on the satellite signal (it would be understandablethat if the location relationship between these mobile devices remainsrelatively stable, the longest time interval may reach 50 seconds.However, if these mobile devices dynamically and randomly join in orleave the current group of mobile devices, an adjustment factor lessthan 1 may be added to this time interval, for example, 0.5. Therefore,the mobile device M needs to calculate its location once, for example,every 50*0.5=25 seconds, based on the satellite signal), therebyreducing the frequency of calculating the location required by locatingservice utilizing the signal received from the satellite.

Therefore, energy consumption is reduced because the mobile device doesnot need to perform a satellite signal-based positioning process thatrequires high energy consumption. Additionally, accuracy of locationestimation by the mobile device may be guaranteed because thecommunication distance supported by the short-range communication israther short (generally less than 10 m).

The basic principle of the present invention has been introduced above.Now, various illustrative non-limiting embodiments of the presentinvention will be described hereinafter.

Illustrative Application Scenario

As mentioned above, the technical solution of the illustrativeembodiments of the present invention is applicable to a scenario whereat least two mobile devices exist in a PAN area within the coverage ofshort-range communication. The scenario as illustrated in FIG. 1 is justan example of such scenario. As illustrated in FIG. 1, the PAN area 102of the mobile device M 101 (for example, provided by Bluetooth or WiFi,etc.) covers a mobile device P 103. The PAN area 104 of the mobiledevice P 103 likewise covers the mobile device M 101. Therefore, themobile device M 101 and the mobile device P 103 can communicateutilizing a short-range communication mechanism (for example, Bluetoothor WiFi, etc.). Further, as illustrated in FIG. 1, the mobile device M101 and the mobile device P 103 may receive signals from theillustrative GPS satellite 105 (not limited to this).

Those skilled in the art may understand that the scenario as illustratedin FIG. 1 is only illustrative. Although FIG. 1 illustrates two mobiledevices, a scenario that comprises more mobile devices is likewiseapplicable to the technical solution according to the illustrativeembodiments of the present invention. Although the scenario illustratedin FIG. 1 takes mobile devices as an example, a scenario comprising aplurality of vehicles that have positioning apparatus and vehiclenetworking apparatusis likewise applicable to the technical solutionaccording to the illustrative embodiments of the present invention.Although FIG. 1 illustrates a global positioning system (GPS) satellite,the satellites adopted by other positioning systems such as Galileo andBeidou are also applicable to the technical solution according to theillustrative embodiments of the present invention.

Illustrative Method

Hereinafter, in combination with the application scenario in FIG. 1 andthe example in FIG. 3, a method for determining the location of a mobiledevice according to the illustrative embodiments of the presentinvention will be described with reference to FIG. 2.

As illustrated in FIG. 2, according to the illustrative embodiments ofthe present invention, method S20, for example, may comprise receivingthe location message from a neighboring device, the location messagecomprising the location of the neighboring mobile device at the currenttime as obtained by the neighboring mobile device through calculationutilizing signals received from satellites (step S201).

Specifically, as illustrated in FIGS. 1 and 3, suppose the mobile deviceM receives the location message from the mobile device P at theT_(P,n+1) time, the location message comprises the accurate locationL_(P) (T_(P,n+1)) at the T_(P,n+1) time obtained by the mobile device Pthrough calculation utilizing the signal received from the satellite.

It should be noted that as mentioned above, each mobile device willreceive signals from the satellite in a certain time interval so as tocalculate its location. According to the illustrative embodiments of thepresent invention, the mobile device M stores in memory means atime-location sequence obtained through calculating the locationutilizing signals received from the satellites, where time-locationsequence may be denoted by<T_(M,1),L_(M)(T_(M,1))>,<T_(M,2),L_(M)(T_(M,2))>, . . .,<T_(M,n),L_(M)(T_(M,n))>, wherein L_(M)(T_(M,k)) denotes the accuratelocation (indicated by vertical line in FIG. 3) of the mobile device Mat the time T_(M,k)(k=1,2, . . . , n) as calculated based on the signalreceived from the satellite, and k denotes that the time of receivingthe satellite signal is the k^(th) time interval. According to theillustrative embodiments of the present invention, the mobile device(for example, mobile device M) also maintains the time-locationsequences obtained through calculating by neighboring mobile devicesbased on the signals received from the satellite for the neighboringmobile devices (for example, mobile device P), where time-locationsequence, for example, is denoted by<T_(P,1),L_(P)(T_(P,1))>,<T_(P,2),L_(P)(T_(P,2))>, . . .,<T_(P,n),L_(P)(T_(P,n))>, wherein L_(P)(T_(P,k)) denotes the accuratelocation (indicated by solid dots in FIG. 3) of the mobile device P atthe time T_(P,k)(k=1,2, . . . , n) as calculated based on the signalreceived from the satellite, k indicates that the time of receiving thesatellite signal is the k^(th) time interval. It would be understandablethat according to the illustrative embodiments of the present invention,each mobile device, after obtaining the accurate location throughcalculation, would send the location message comprising the accuratelocation to other mobile devices within its PAN area via a short-rangecommunication mechanism. Accordingly, the other mobile devices thatreceive this location message may store in a memory the time-locationsequence for the mobile device. Further, it is seen from FIG. 3 that then+1 time interval of the mobile device M is before the (n+1)^(st) timeinterval of the neighboring mobile device P. Namely, first, the mobiledevice M receives satellite signals and calculates its location, andthen the mobile device P receives the satellite signals and calculatesits location. It should be noted that the length of the locationsequence (i.e., time-location sequence) maintained by the mobile deviceM and obtained through calculation utilizing the satellite signal may beindependent of the length of the location sequence (i.e., time-locationsequence) received from the neighboring mobile device P. The lengths ofthe two sequences may not be equal, thus, the subscript n is alsodifferent in each sequence.

Those skilled in the art would also appreciate that the location messagemay be any existing message that is capable of carrying an accuratelocation of a mobile device or a message specifically designed forimplementing the embodiments of the present invention. Different messageformats and transmission methods have no limitation on the presentinvention.

According to the illustrative embodiments of the present invention, themethod S20 for example may further comprise estimating the location ofthe mobile device at the current time based on the stored locations ofthe mobile device at historical time, the stored locations of theneighboring mobile device at historical time, and the received locationof the neighboring mobile device at the current time (step S203).

Specifically, as illustrated in FIGS. 1 and 3, the mobile device Mestimates the location of the mobile device M at the current time (forexample, EL_(M) (T_(P,n+1)) as illustrated in FIG. 3) based on thestored locations of the mobile device M at historical time (for example,the EL_(M) (T_(P,n)) as illustrated in FIG. 3, i.e., the estimatedlocation), a stored location of the neighboring mobile device P at ahistorical time (for example, L_(P) (T_(P,n)) as illustrated in FIG. 3),and the received location of the neighboring mobile device Pat thecurrent time (L_(P)(T_(P,n+1)).

Next, a more detailed process regarding determining the location of themobile device M at the current time will be further described.

It should be understood that if a relative displacement between themobile device M and the mobile device P at the current time can bedetermined, then the location of the mobile device M at the current timemay be determined more accurately based on the accurate location of themobile device P at the current time plus the relative displacement. Ofcourse, those skilled in the art may understand that this manner ismerely illustrative, and the present invention is not limited thereto.Any manner of estimating the location of the mobile device at thecurrent time based on the location of the mobile device at a historicaltime, the location of a neighboring mobile device at the historicaltime, and the location of the neighboring mobile device at the currenttime may be applicable to the present invention.

In view of the above analysis, according to the illustrative embodimentsof the present invention, step S203 for example may comprise obtainingthe relative displacement between the mobile device M and theneighboring mobile device P at the current time; and calculating a sumof the received location of the neighboring mobile device P at thecurrent time and the relative displacement at the current time, as thelocation of the mobile device M at the current time, which is denoted byEL¹ _(M)(t)=L_(P)(t)+D(M−>P), wherein EL^(t) _(M)(t) denotes theestimated location of the mobile device M at the time t (because itwould be described hereinafter that the mobile device M estimates thelocation at t time (denoted by EL² _(M)(t)) using its own trajectory,the EL¹ _(M)(t) is used to denote the location at t time estimated bythe mobile device M utilizing the trajectory of the neighboring mobiledevice P. It would be understood that the numerical signs 1 and 2 hereare only for distinguishing, without creating any limitation to thepresent invention), L_(P)(t) denotes the accurate location of the mobiledevice P at t time, while D(M−>P) denotes the relative displacementbetween the mobile device M and the mobile device P at t time.

Hereinafter, a process of obtaining the relative displacement at thecurrent time between mobile devices will be described in detail withreference to specific examples.

Suppose the Relative Displacement Does Not Change

The inventors find that if the relative displacement between the mobiledevice M and the mobile device P will not change during a certain periodof time and the relative displacement between the mobile device M andthe mobile device P at a certain or some historical times may bedetermined, then the relative displacement of the certain or somehistorical times may be used as the relative displacement at the currenttime between the two mobile devices. In other words, the location of themobile device M at the current time may be estimated more accuratelybased on the accurate location of the mobile device P at the currenttime plus the relative displacement at a certain or some historicaltime.

It would be understandable that, for example, if the users of the mobiledevices M and P are both in a moving fixed space (for example, a crowdedsubway taken by the users), the relative displacement therebetweenremains nearly unchanged during a rather long period of time. In thisscenario, the embodiment of this supposedly unchanged relativedisplacement may be applied.

As far as the mobile device M is concerned, whether the relativedisplacement between the two remains unchanged may be checked bycomparing the stored time-location sequence of the mobile device M andthe time-location sequence of the neighboring mobile device P.

It is seen from the above analysis that according to the illustrativeembodiments of the present invention, the step of obtaining, forexample, may comprise: calculating the relative displacement (i.e.,D(M−>P, T_(P,n))) between the mobile device M and the neighboring mobiledevice P at a same historical time based on the stored location of themobile device M (for example, EL_(M)(T_(P,n)) as illustrated in FIG. 3)at the historical time and the stored location of the neighboring mobiledevice P (for example, L_(P)(T_(P,n)) as illustrated in FIG. 3) at thehistorical time, as the relative displacement therebetween at thecurrent time (D(M−>P, T_(P,n+1))), wherein, D(M−>P,T_(P,n))=EL_(M)(T_(P,n))−L_(P)(T_(P,n)), namely, at the n^(th) timeinterval of the neighboring mobile device P, the relative displacementbetween the mobile device M and the neighboring mobile device P.

According to some other embodiments of the present invention, theobtaining step, for example, may comprise calculating relativedisplacements (for example, D(M−>P, T_(P,n)) and D(M−>P, T_(M,n)), etc.)between the mobile device M and the neighboring mobile device P at aplurality of same historical times based on the stored locations of themobile device M at the historical times (for example, L_(M)(T_(P,n)),L_(M)(T_(M,n)) and the like as illustrated in FIG. 3) and the storedlocations of the neighboring mobile device P at the historical times(for example, L_(P)(T_(P,n)) as illustrated in FIG. 3, andEL_(P)(T_(M,n)) as not illustrated in FIG. 3); and calculating anaverage value of the relative displacements at the plurality of samehistorical times (for example, [D(M−>P, T_(P,n))+D(M−>P, T_(M,n))]/2),as the relative displacement (D(M−>P, T_(P,n+1))) therebetween at thecurrent time. It may be understood that some locations per se athistorical times may be estimated values. Thus, in one embodiment, somehistorical errors are introduced when calculating the relativedisplacements. The advantage of calculating the average value of therelative displacements at a plurality of historical times is that it mayreduce error, thereby improving the accuracy of determining the relativedisplacement at a historical time.

According to some other illustrative embodiments of the presentinvention, after adopting a plurality of estimated values of location,the mobile device M may immediately calculate its own accurate locationafter receiving the signal from the satellite after receiving theaccurate location of the neighboring mobile device P at a certain time.In subsequent calculation of location estimation, the difference betweenthese two accurate locations may be used as the relative displacement atthe current time therebetween, thereby further improving the accuracy ofdetermining the relative displacement at the historical time.

Suppose the Relative Velocity Does Not Change

The inventors find that if the relative velocity between the mobiledevice M and the mobile device P does not change during a certain periodof time and the relative velocity between the mobile device M and themobile device P at a certain historical time can be determined, then therelative displacement at this certain historical time may be used as abase, and _(t)he relative displacement at the current time therebetweenmay be obtained on this basis plus the increased relative displacementbetween the two mobile devices at the time difference between thehistorical time and the current time. In other words, the location ofthe mobile device M at the current time may be estimated more accuratelyon the basis of the accurate location of the mobile device P at thecurrent time plus the relative displacement at the certain historicaltime as well as the relative displacement increased between thehistorical time and the current time with the elapse of time.

As far as the mobile device M is concerned, the velocities of the mobiledevice M and the neighboring mobile device P may be obtainedrespectively through the stored time-location sequence of the mobiledevice M and the stored time-location sequence of the neighboring mobiledevice P, and whether the relative velocity therebetween maintainsunchanged is checked by comparing the relative velocities.

It may be seen from the above analysis that according to theillustrative embodiments of the present invention, the obtaining step,for example, may comprise: calculating the relative displacement (i.e.,D (M−>P, T_(P,n))) between the mobile device M and the neighboringmobile device P at a same historical time based on the stored locationof the mobile device M at the historical time (for exampleEL_(M)(T_(P,n)) as illustrated in FIG. 3) and the stored location of theneighboring mobile device P at the historical time (for example,L_(P)(T_(P,n)) as illustrated in FIG. 3); calculating a product of therelative velocity between the mobile device M and the neighboring mobiledevice P (V(M−>P) and the difference between the current time and thesame historical time (Δt=T_(P,n+1)−T_(P,n)); and calculating a sum ofthe relative displacement (D(M−>P, T_(P,n)) at the same historical timeand the product (V(M−>P)*Δt), as the relative displacement (D(M−>P,T_(P,n+))) therebetween at the current time, namely, D(M−>P,T_(P,n+1))=D(M−>P,T_(P,n))+V(M−>P)*Δt.

According to the illustrative embodiments of the present invention, thehistorical time prefer the latest time (for example, T_(P,n) asillustrated in FIG. 3) when the neighboring mobile device P obtained thelocation through calculation utilizing the signal received from thesatellite.

It is seen from the above depiction that if it is assumed that therelative velocity remains unchanged, it is required to obtain therelative velocity between the mobile device M and the neighboring mobiledevice P at historical time.

According to the illustrative embodiments of the present invention, therelative velocity may be obtained through the following steps:calculating respective velocities(V_(M)=[L_(M)(T_(M,n+1))−L_(M)(T_(P,n)]/[T_(M,n+1)−T_(P,n)];V_(P)=[EL_(P)(T_(M,n+1))−L_(P)(T_(P,n))]/[T_(M,n−1)−T_(P,n)]) of themobile device M and the neighboring mobile device P based on therespective displacements of the mobile device M and the neighboringmobile devices P (for example L_(M)(T_(M,n+1))−EL_(M)(T_(P,n));EL_(P)(T_(M,n+1))−L_(P)(T_(P,n))) at their respective historical timesand based on the time difference between the historical times (forexample, T_(M,n+1)−T_(P,n)); and calculating the difference between thevelocity of the mobile device M and that of the neighboring mobiledevice P, as the relative velocity (V(M−>P)=V_(M)−V_(P)).

Of course, those skilled in the art may understand that the averagevelocity at a plurality of periods of time may be calculated as thevelocity value, which may achieve a more accurate location estimationeffect.

Position Calibration

It may be seen from FIG. 3 that the mobile device M likewise stores itsown time-location sequence. It would be understandable that the mobiledevice M may also estimate its location at T_(P,n+1) based on its ownhistorical trajectory.

According to the illustrative embodiments of the present invention, thisestimation, for example, may comprise calculating the sum of thefollowing two: the latest location (L_(M)(T_(M,n+1))) obtained by themobile device M through calculation utilizing a signal received from thesatellite; and a product of the velocity (V_(M)) of the mobile device Mand the difference (T_(P,n+1)−T_(M,n+1)) between the latest time whenthe mobile device M obtained the location through calculation utilizingthe signal received from the satellite and the current time. In otherwords, the location of the mobile device M at the current time (in thisexample, indicated by EL² _(M)(T_(P,n+1))) may be estimated based on thelocation at the latest historical time plus the displacement experiencedwithin Δt time, which is denoted as EL²_(M)(T_(P,n+1))=L_(M)(T_(M,n+1))+V_(M)*(T_(P,n+1)−T_(M,n+1)).

The inventors find that the estimated location may be used to calibratethe location of the mobile device M at the current time as estimated bymeans of the neighboring mobile device P. In other words, a weighted sumof the two estimated locations may be calculated, wherein the sum of theweights of the two is 1. Further, the mobile device M may determinewhose trajectory stability is much stronger based on the storedhistorical trajectory of its own and the historical trajectory of themobile device P and then grants a higher weight to the estimatedlocation as obtained utilizing the more stable trajectory. It would beunderstandable that the calibrated estimated location may reflect thecurrent location of the mobile device M more accurately, which isdenoted as EL_(M)(T_(P,n+1))=α*EL¹ _(M) (T_(P,n+1))+(1−α)*EL²_(M)(T_(P,n+1)), wherein α (0<α<1) is a configurable factor foradjusting the weight between the two estimations.

Other Enhancements

As mentioned above, the more mobile devices capable of supporting thepositioning and short-range communication mechanism exist within the PANarea of the mobile device M, the longer is the time interval required bythe mobile device M to calculate its own accurate location throughreceiving a signal from the satellite. According to the illustrativeembodiments of the present invention, an actual location calculationinterval may, for example, be based on a shortest location calculationinterval, a total number of neighboring mobile devices, and an adjustingfactor, wherein the location calculation interval indicates the timeinterval between the times of calculating the location utilizing thesignal received from the satellite.

For example, suppose 9 similar mobile devices exist in the PAN area ofthe mobile device M. If the mobile device M needs to calculate thelocation once every 5 seconds utilizing the satellite signal in theprior art, then, after the technical solution of the present inventionis applied, it only needs to calculate the accurate location once every50 seconds to the utmost utilizing the satellite signal (as illustratedabove). In other words, now, the longest actual location calculationtime interval is 50 seconds. Therefore, it achieves an effect ofreducing the frequency of calculating the location required by alocating service utilizing a signal received from the satellite.

Besides, according to the embodiments of the present invention, thelocation message, for example, may further comprise a uniqueidentification of the neighboring mobile device.

According to the illustrative embodiments of the present invention, thetotal number of neighboring mobile devices is determined through thefollowing manner: sending finding messages to neighboring mobiledevices, and counting the replies from the neighboring mobile devices inresponse to the finding messages, as the total number of neighboringmobile devices. For example, a mobile device broadcasts findingmessages, and the number of responses from neighboring mobile devices isjust the number of the neighboring mobile devices. It should beunderstood that the finding message may be any message that is capableof triggering the mobile devices that receive the message to return aresponse. The format, transmission and reception of the finding messagedo not constitute a limitation to the present invention, which may beimplemented by any existing message delivery mechanism.

Alternatively, according to the illustrative embodiments of the presentinvention, the total number of neighboring mobile devices, for example,is determined through the following manner: the mobile device may, forexample, receive location messages sent from neighboring mobile devicestill the unique identification of a neighboring mobile device isrepeated; and counting these location messages as the total number ofneighboring mobile devices. As mentioned above, neighboring mobiledevices may send location messages in a substantially even timeinterval. Suppose the mobile device receives the location message fromthe first mobile device again after receiving the 9^(th) locationmessage, then it indicates that all surrounding neighboring mobiledevices have already sent a location message, then the number of the 9location messages is just the number of the neighboring mobile devices.

According to the illustrative embodiments of the present invention, themobile device, for example, may store in association the receivedlocation of a neighboring mobile device at the current time, the currenttime, and the unique identification of the neighboring mobile device,i.e., forming a time-location sequence as above mentioned.

According to illustrative embodiments of the present invention, if themobile device detects a change of the total number of the neighboringmobile devices (for example, the number of received location messageschanges within a reasonable period of time), the method S20 may forexample further include: in response to the change of total number ofneighboring mobile devices, receiving a signal from the satellite andcalculating the location of the mobile device at this time (i.e., thetime when the total number of neighboring mobile devices changes); andsending the location of the mobile device at this time to theneighboring mobile devices. The advantage of this operation is that whenthe number of the neighboring mobile devices changes, each mobile deviceshould contribute to its neighboring mobile devices in calculating thelocation, i.e., sharing the accurate location calculated by itself atthe current time with its neighboring mobile devices, thereby enhancingthe accuracy of determining the location.

According to the illustrative embodiments of the present invention, themobile device receives a signal from the satellite and calculates thelocation during a random time between 0 time (0 time indicates the timewhen the mobile device starts initiating the method of the presentinvention or the time of obtaining the location which is latestcalculated by the neighboring device) and the above actual locationcalculation time interval (for example, 50 seconds to the utmost); andsending the location to the neighboring mobile device. The advantage ofthis operation is to further contribute to the neighboring mobiledevices in calculating locations, and randomizing the time when eachmobile device receives the satellite signals.

Illustrative Apparatus

After introducing the method according to the illustrative embodimentsof the present invention, next, detailed description will be made to anapparatus (hereinafter, referred to as location determining apparatus400) for determining the location of a mobile device according toillustrative embodiments of the preset invention with reference to FIG.4.

As illustrated in FIG. 4, the location determining apparatus 400, forexample, may comprise: location message receiving means 401 configuredto receive the location message from a neighboring mobile device, thelocation message comprising the location of the neighboring mobiledevice obtained by the neighboring mobile station through calculationutilizing a signal received from a satellite; and location estimatingmeans 403 configured to estimate the location of the mobile device atthe current time based on a stored location of the mobile device at ahistorical time, a stored location of the neighboring mobile device atthe historical time, and the received location of the neighboring mobiledevice at the current time.

According to the illustrative embodiments of the present invention, thelocation estimating means 403, for example, may comprise: relativedisplacement obtaining means 4031 configured to obtain a relativedisplacement between the mobile device and the neighboring mobile deviceat the current time; and location calculating means 4032 configured tocalculate a sum of the received location of the neighboring mobiledevice at the current time and the relative displacement at the currenttime, as the location of the mobile device at the current time.

According to the illustrative embodiments of the present invention, therelative displacement obtaining means 4031, for example, may comprisemeans for calculating a relative displacement between the mobile deviceand the neighboring mobile device at a same historical time based on thestored location of the mobile device at the historical time and thestored location of the neighboring mobile device at the historical time,as the relative displacement at the current time.

According to the illustrative embodiments of the present invention, therelative displacement obtaining means 4031, for example, may comprisemeans for calculating relative displacements of the mobile device andthe neighboring mobile device at a plurality of same historical timesbased on the stored locations of the mobile device at the historicaltimes and the stored locations of the neighboring mobile device at thehistorical times; and means for calculating an average value of therelative displacements at the plurality of same historical times, as therelative displacement at the current time.

According to the illustrative embodiments of the present invention, therelative displacement obtaining means 4031, for example, may comprisemeans for calculating a relative displacement between the mobile deviceand the neighboring mobile device at a same historical time based on thestored location of the mobile device at the historical time and thestored location of the neighboring mobile device at the historical time;means for calculating a product of a relative velocity between themobile device and the neighboring mobile device with the differencebetween the current time and the same historical time; and means forcalculating a sum of the relative displacement at the same historicaltime and the product, as the relative displacement at the current time.

According to the illustrative embodiments of the present invention, thesame historical time, for example, may be the latest time when theneighboring mobile device obtained the location through calculationutilizing the signal received from the satellite.

According to the illustrative embodiments of the present invention, thelocation determining apparatus 400, for example, may further comprisemeans for determining a relative velocity based on the following:calculating respective velocities of the mobile device and theneighboring mobile device based on the displacement of the mobile devicebetween locations of the mobile device at its historical times and thedisplacement of the neighboring mobile device between locations of theneighboring mobile device at its respective historical times andrespective time difference between the historical times; and calculatinga difference between the velocity of the mobile device and the velocityof the neighboring mobile device, as the relative velocity.

According to the illustrative embodiments of the present invention, thelocation determining apparatus 400, for example, may further comprise:means for calculating a weighted sum of the location of the mobiledevice at the current time and two of the following, as the location ofthe mobile device at the current time: the location of the mobile deviceas obtained by the latest calculation utilizing the signal received fromthe satellite; and a product of the velocity of the mobile device andthe difference between the latest time when the mobile device obtainedthe location through calculation utilizing the signal received from thesatellite and the current time.

According to the illustrative embodiments of the present invention, thelocation determining apparatus 400, for example, may further comprisemeans for determining an actual location calculation interval based on ashortest location calculation interval, a total number of neighboringmobile devices, and an adjusting factor, wherein the locationcalculation interval indicates the time interval between the times ofcalculating the location utilizing the signal received from thesatellite.

According to the illustrative embodiments of the present invention, thelocation message further comprises a unique identification of aneighboring mobile device, and the location determining apparatus 400further comprises means for determining the total number of neighboringmobile devices through the following manner: sending finding messages toneighboring mobile devices, and counting the replies from theneighboring mobile devices in response to the finding messages, as thetotal number of the neighboring mobile devices; or receiving locationmessages sent from neighboring mobile devices till a uniqueidentification of a neighboring mobile device repeats, and counting thelocation messages, as the total number of neighboring mobile devices.

According to illustrative embodiments of the present invention, thelocation determining apparatus 400, for example, may further comprise:storing means configured to store the received location of theneighboring mobile device at the current time, the current time, and theunique identification of the neighboring mobile device in association.

According to the illustrative embodiments of the present invention, ifthe total number of neighboring mobile devices changes, the locationdetermining apparatus 400, for example, may further comprise: means forreceiving a signal from a satellite and calculating the location of themobile device at the current time in response to the change of totalnumber of neighboring mobile devices; and means for sending the locationof the mobile device at the current time to the neighboring mobiledevices.

According to the illustrative embodiments of the present invention, thelocation determining apparatus 400, for example, may further comprise:means for receiving a signal from a satellite and calculating thelocation at a random time from 0 time to the actual location calculationinterval; and means for sending the location to the neighboring mobiledevices.

Illustrative Mobile Device

Finally, FIG. 5 schematically illustrates a block diagram of a mobiledevice 10 that benefits from the illustrative embodiments of the presentinvention and may be the illustrative apparatus according to theillustrative embodiments of the present invention. However, it should beunderstood that the mobile phone as illustrated in this figure anddescribed hereinafter is only an example of a class of mobile devicesthat benefit from the illustrative embodiments of the present invention,instead of limiting the scope of the illustrative embodiments of thepresent invention. Although a plurality of embodiments of the mobiledevice 10 have been illustrated for the illustrative purpose, forexample, a portable digital assistant (PDA), pager, mobile TV, gamingdevice, laptop, camera, video camera, audio/video player, radio, GPSdevice, or any other type of mobile device with any combination of theabove, as well as other type of voice and textual communication system,may easily employ the illustrative embodiments of the present invention.

In addition, although the mobile device 10 may employ the plurality ofembodiments of the method of the present invention, an apparatus otherthan the mobile device may also employ the method of the illustrativeembodiments of the present invention. Further, although the method andapparatus according to the illustrative embodiments of the presentinvention have been described above mainly with reference to the mobilecommunication application, it should be understood that the method andapparatus according to the illustrative embodiments of the presentinvention may be applied in the mobile communication business and beyondthe mobile communication business in combination with various otherapplications.

The mobile device 10 may comprise an antenna 12 (or a plurality ofantennas) operatively communicating with a transmitter 14 and a receiver16. The mobile device 10 may further comprise means configured toprovide signals to the transmitter 14 and receive signals from thereceiver 16, respectively, for example, the controller 20 or otherprocessing unit. The signal comprises a signaling message applicable tothe cellular system air interface standard, as well as user voice,received data and/or user generated data. In this regard, the mobiledevice 10 may be operated utilizing one or more air interface standards,communication protocol, modulation type, and access type. For example,the mobile device 10 may operate according to any communication protocolamong a plurality of first generation, second generation, thirdgeneration and/or fourth generation, and other communication protocols.For example, the mobile device 10 may operate according to the secondgeneration (2G) wireless communication protocol IS-136 (time divisionmultiple access (TDMA)), GSM (global mobile communication system) andIS-95 (code division multiple access), or according to the thirdgeneration (3G) wireless communication protocol such as universal mobiletelecommunications system (UMTS), CDMA2000, wideband CDMA (WCDMA) andtime division-synchronization TDMA (TD-SCDMA), or according to the 3.9generation (3.9G) wireless communication protocol such as evolveduniversal terrestrial radio access network (E-UTRAN), or according thefourth generation (4G) wireless communication protocol. Instead (or inexclusion), the mobile device 10 may operation according to anon-cellular communication mechanism. For example, the mobile device 10may communication in a wireless local area network (WLAN) or othercommunication network. In addition, the mobile device 10 may communicateaccording to any of the following technologies, such as radio frequency(RF), infrared ray (IrDA) or a plurality of different wirelessnetworking technologies (including WLAN technologies, such as IEEE802.11 (for example, 802.11a, 802.11b, 802.11g, 802.11n, etc.), a globalmicrowave access interoperability (WiMAX) technology, such as IEEE802.16 and/or wireless personal area network (WPAN) technology, forexample, IEEE 802.15, Bluetooth (BT), ultra wideband (UWB) and/orsimilar technology

It should be understood that means like controller 20 may comprise acircuit for implementing the audio and logic functions of the mobiledevice 10. For example, the controller 20 may comprise a digital signalprocessor device, a micro-processor device, and various A/D converters,D/A converters, and other support circuits. The control and signalprocessing functions of the mobile device 10 are allocated among thesedevices based on their corresponding capabilities. Therefore, thecontroller 20 may comprise a function of performing convolutional codingand interleave to the message and data before modulation andtransmission. The controller 20 may further comprise an internal voiceencoder and may comprise an interval data modem. In addition, thecontroller 20 may comprise a function of operating one or more softwareprograms stored in a memory. For example, the controller 20 may operatea connectivity program, for example, a conventional Web browser. Theconnectivity program may then allow the mobile device 10 to transmit andreceive Web contents for example according to a wireless applicationprotocol (WAP), a hypertext transfer protocol (HTTP) and/or a similarprotocol, for example, location-based content and/or other webpagecontent.

The mobile device 10 may further comprise a user interface thatcomprises all output devices connected to the controller 20, forexample, a conventional earphone or speaker 24, a ringer 22, amicrophone 26, a display 28, and a user input device. A user inputinterface allowing the mobile device 10 to receive data may comprise anydevice in a plurality of devices that allow the mobile device 10 toreceive data, for example, a keypad 30, a touch display (not shown) andother input device. In an embodiment comprising a keypad 30, the keypad30 may comprise conventional digital keys (0-9) and associated keys (#,*) and other hard keys and soft keys for operating the mobile device 10.Instead, the keypad 30 may comprise a conventional QWERTY keypadarrangement. The keypad 30 may also comprise various kinds of soft keyshaving association functions. In addition or instead, the mobile device10 may further comprise an interface device such as a joystick or otheruser input devices. The mobile device 10 further comprises variouscircuit power supplies required for operating the mobile device 10 andalternatively a battery 34 that may provide mechanical vibration asdetectable output, for example, a vibrating battery package.

The mobile device 10 may further comprise a user identification module(UIM) 38. The UIM 38 is usually a memory device with a processor builtin. The UIM 38 may for example comprise a user identification module(SIM), a universal integrated circuit card (UICC), a universal useridentification module (USIM), or a removable user identification module(R-UIM), etc. The UIM 38 always stored an information element associatedwith the mobile user. Besides UIM 38, the mobile device 10 may befurther provided with a memory. For example, the mobile device 10 maycomprise a volatile memory 40, for example, comprising a volatile randomaccess memory (RAM) of a cache memory for temporarily storing data. Themobile device 10 may also comprise other non-volatile memory 42 that isembedded or removable. In addition or instead, the non-volatile memory42 may also comprise an electrically erasable programmable read-onlymemory (EEPROM), a flash, etc. For example, the non-volatile memory maybe available from the SanDisk of Sunnyvale, Calif., or Lexar Media ofFremont, Calif. The memory may store any information and data in aplurality of pieces of information and data available for the mobiledevice 10 for implementing the functions of the mobile device 10. Forexample, the memory may comprise an identifier that is capable ofuniquely identifying the mobile device 10, for example, theinternational mobile equipment identity (IMEI) code, and may store thereceived current time-locations of the neighboring mobile devices andthe current time and the unique identification of the neighboringdevices in association. Specifically, the memory may store anapplication that is executed by the controller 20, the controllerdetermining the current location of the mobile device 10.

The mobile device 10 may further comprise a positioning sensor 36 thatcommunicates with the controller 20, for example, a global positioningsystem (GPS) module. The positioning sensor 36 may be any apparatus,device or circuit for performing location determination so as toposition the mobile device 10. The positioning sensor 36 may compriseall hardware for performing location determination so as to position themobile device 10. Alternatively or additionally, the positioning sensor36 may store the instructions executed by the controller 20 utilizing amemory device of the mobile device 10, and its storage manner issoftware required for determining the location of the mobile device 10.Apparently, this illustrative positioning sensor 36 may be a GPS module.However, the positioning sensor 36 may comprise or alternatively beimplemented as for example an auxiliary global positioning system(auxiliary GPS) sensor or positioning client. The auxiliary GPS sensoror positioning client may communicate with a network device such as anair or ground sensor so as to receive and/or send a message used fordetermining the location of the mobile device 10. In this regard,locating of the mobile device 10 may be determined by for example theabove GPS, cell ID, signal triangle measurement, or other mechanisms. Inone illustrative embodiment, the positioning sensor 36 comprises apedometer or an inertia sensor. Therefore, the positioning sensor 36 maydetermine the location of the mobile device 10, for example, withreference to the longitude and latitude directions as well as heightdirection of the mobile device 10, or positioning with respect to areference point, for example, a target point or a start point. Then, theinformation from the positioning sensor 36 may be transmitted to thememory of the mobile device 10 or another memory device, so as to bestored as positioning history or location information. In addition, thepositioning sensor 36 may transmit/receive location information via thetransmitter 14/receiver 16 utilizing the controller 20, for example,locating of the mobile device 10.

The structural block diagram in FIG. 5 is shown only for illustrationpurpose, and is not intended to limit the invention. In some cases, somedevices can be added or reduced as required.

Embodiments of the present invention can be implemented with software,hardware or the combination thereof. The hardware part can beimplemented by a dedicated logic; the software part can be stored in amemory and executed by a proper instruction execution system such as amicroprocessor or a dedicated designed hardware. The normally skilled inthe art may understand that the above method and apparatus may beimplemented with computer-executable instructions and/or in processorcontrolled codes, for example, such code is provided on a bearer mediumsuch as a magnetic disk, CD, or DVD-ROM, or a programmable memory suchas a read-only memory (firmware) or a data bearer such as an optical orelectronic signal bearer, The apparatuses and their modules in thepresent invention may be implemented by hardware circuitry of aprogrammable hardware device such as a very large scale integratedcircuit or gate array, a semiconductor such as logical chip ortransistor, or a field-programmable gate array, or a programmablelogical device, or implemented by software executed by various kinds ofprocessors, or implemented by combination of the above hardwarecircuitry and software.

It should be noted that although a plurality of means or sub-means ofthe location determining apparatus have been mentioned in the abovedetailed depiction, such division is merely non-compulsory. Inactuality, according to the embodiments of the present invention, thefeatures and functions of the above described two or more means may beembodied in one means. In turn, the features and functions of the abovedescribed one means may be further embodied in more means.

Besides, although operations of the present invention method aredescribed in a particular order in the drawings, it does not require orimply that these operations must be performed according to thisparticular sequence, or a desired outcome can only be achieved byperforming all shown operations. On the contrary, the executionsequences for the steps as depicted in the flowcharts may change.Additionally or alternatively, some steps may be omitted, a plurality ofsteps may be merged into one step, or a step may be divided into aplurality of steps for execution.

Although the present invention has been depicted with reference to aplurality of embodiments, it should be understood that the presentinvention is not limited to the disclosed embodiments. On the contrary,the present invention intends to cover various modifications andequivalent arrangements included in the spirit and scope of the appendedclaims. The scope of the appended claims meets the broadest explanationsand covers all such modifications and equivalent structures andfunctions.

1. A method for determining a location of a mobile device, comprising:calculating a location of a neighboring mobile device at a current timeby utilizing a signal received from a satellite; receiving a locationmessage from the neighboring mobile device, wherein the location messagecomprises the location of the neighboring mobile device; and estimatinga location of the mobile device at a current time based on thefollowing: (i) stored locations of the mobile device at a historicaltime, (ii) stored locations of the neighboring mobile device at ahistorical time, and (iii) the received location of the neighboringmobile device at the current time.
 2. The method according to claim 1,wherein estimating the location of the mobile device at the current timecomprises: obtaining a relative displacement between the mobile deviceand the neighboring mobile device at the current time; and calculatingthe location of the mobile device at the current time as a sum of thereceived location message of the neighboring mobile device at thecurrent time and the relative displacement at the current time.
 3. Themethod according to claim 2, wherein obtaining the location of themobile device at the current time comprises: calculating the relativedisplacement at the current time as a relative displacement between themobile device and the neighboring mobile device at a same historicaltime based on the stored locations of the mobile device at thehistorical time and the stored locations of the neighboring mobiledevice at the historical time.
 4. The method according to claim 2,wherein obtaining the location of the mobile device at the current timecomprises: calculating a plurality of relative displacements between themobile device and the neighboring mobile device at a plurality of samehistorical times based on a plurality of stored locations of the mobiledevice at the plurality of same historical times and a plurality of thestored locations of the neighboring mobile device at the plurality ofhistorical times; and calculating the relative displacement at thecurrent time as an average value of the plurality of relativedisplacements at the plurality of same historical times.
 5. The methodaccording to claim 2, wherein obtaining the location of the mobiledevice at the current time comprises: calculating the relativedisplacement between the mobile device and the neighboring mobile deviceat a same historical time based on a plurality of stored locations ofthe mobile device at the historical time and based on a plurality ofstored locations of the neighboring mobile device at the same historicaltime; calculating a product of a relative velocity between the mobiledevice and the neighboring mobile device and a difference between thecurrent time and the same historical time; and calculating the relativedisplacement at the current time as the sum of the relative displacementat the same historical time and the product.
 6. The method according toclaim 5, wherein the same historical time is a latest time when theneighboring mobile device obtained the location from calculating thelocation of a neighboring mobile device at the current time by utilizingthe signal received from the satellite.
 7. The method according to claim5, wherein the relative velocity is calculated based on the following:calculating a plurality of velocities of the mobile device and theneighboring mobile device based on a displacement of the mobile devicebetween a plurality of locations of the mobile device at a plurality ofhistorical times and based on a displacement of the neighboring mobiledevice between the locations of the neighboring mobile device at theplurality of historical times and a plurality of time differencesbetween the historical times of the neighboring mobile device; andcalculating the relative velocity as a difference between a velocity ofthe mobile device and a velocity of the neighboring mobile device. 8.The method according to claim 2, further comprising: calculating thelocation of the mobile device at the current time, wherein the locationof the mobile device at the current time comprises a weighted sum of thefollowing: a location of the mobile device at the current time; alocation obtained by the mobile device at a latest time which is,calculated utilizing the signals received from the satellite; and aproduct of a velocity of the mobile device; and a difference between thelocation of the mobile device at the current time and the location ofthe mobile device at the latest time which is calculated utilizing thesignal received from the satellite.
 9. The method according to claim 1,further comprising: determining an actual location calculation intervalbased on the following: (i) a shortest location calculation interval,(ii) a total number of neighboring mobile devices, and (iii) anadjusting factor, wherein the location calculation interval indicates aninterval between times which are calculated utilizing signals receivedfrom the satellite.
 10. The method according to claim 9, wherein thelocation message further comprises a unique identification of theneighboring mobile device; and wherein determining total number of theneighboring mobile devices is comprises: sending a plurality of findingmessages to the neighboring mobile devices; and counting from theneighboring mobile devices in response to the plurality of findingmessages, wherein the plurality of replies is counted as the totalnumber of the neighboring mobile devices.
 11. The method according toclaim 10, further comprising: storing in an association comprising thereceived location of the neighboring mobile device at the current time,(ii) the current time, (iii) and the unique identification of theneighboring mobile device.
 12. The method according to claim 9, furthercomprising: receiving a plurality of signals from the satellite;calculating the location of the mobile device at the current time, inresponse to a change of the total number of the neighboring mobiledevices; and sending the location of the mobile device at the currenttime to the neighboring mobile devices.
 13. The method according toclaim 12, further comprising: receiving the signal from the satelliteand calculating the location at a random time between time 0 and theactual location calculation interval; and sending the location to theplurality of neighboring mobile devices.
 14. An apparatus fordetermining a location of a mobile device, comprising: calculating meansconfigured to calculate a location of a neighboring mobile device at acurrent time by utilizing a signal received from a satellite; locationmessage receiving means configured to receive the location message fromthe neighboring mobile device, wherein the location message comprisesthe location of the neighboring mobile device at a current time; andlocation estimating means configured to estimate a location of themobile device at the current time based on the following: (i) storedlocation of the mobile device at a historical time, (ii) a storedlocation of the neighboring mobile device at the historical time, and(iii) the received location of the neighboring mobile device at thecurrent time.
 15. The apparatus according to claim 14, wherein thelocation estimating means comprises: relative displacement obtainingmeans configured to obtain a relative displacement between the mobiledevice and the neighboring mobile device at the current time; andlocation calculating means configured to calculate the location of themobile device at the current time as a sum, wherein the sum comprisesthe received location of the neighboring mobile device at the currenttime and the relative displacement at the current time.
 16. Theapparatus according to claim 15, wherein the relative displacementobtaining means comprises: means for calculating the relativedisplacement at the current time as a relative displacement between themobile device and the neighboring mobile device at a same historicaltime, wherein the relative displacement comprises the stored location ofthe mobile device at the historical time and the stored location of theneighboring mobile device at the historical time.
 17. The apparatusaccording to claim 15, wherein the relative displacement obtaining meanscomprises: means for calculating a plurality of relative displacementsbetween the mobile device and a plurality of neighboring mobile devicesat a plurality of same historical times based on a plurality of storedlocations of the mobile device at a plurality of historical times andthe plurality of stored locations of the neighboring mobile device atthe plurality of same historical times; and means for calculating therelative displacement at the current time as an average value of theplurality of relative displacements at the plurality of same historicaltimes.
 18. The apparatus according to claim 15, wherein the relativedisplacement obtaining means comprises: means for calculating a relativedisplacement between the mobile device and the neighboring mobile deviceat a same historical time based on the stored location of the mobiledevice at a plurality of historical times and based on the storedlocation of the neighboring mobile device at the same historical time;means for calculating a product of a relative velocity between themobile device and the neighboring mobile device; means for calculating adifference between the current time and the same historical time; andmeans for calculating the relative displacement at the current time as asum of the relative displacement at the same historical time and theproduct.
 19. The apparatus according to claim 18, wherein the samehistorical time is the latest time when the neighboring mobile deviceobtained a location which is calculated utilizing the signal receivedfrom the satellite.
 20. The apparatus according to claim 18, furthercomprising means for determining the relative velocity based on thefollowing: calculating a plurality of respective velocities of themobile device and the neighboring mobile device which is based on thedisplacement of the mobile device between a plurality of locations ofthe mobile device at a plurality of historical times and thedisplacement of the neighboring mobile device between the plurality oflocations of the neighboring mobile devices at the plurality ofhistorical times and a plurality of time differences between thehistorical times; and calculating a plurality of relative velocities asa difference between the velocity of the mobile device and the velocityof the neighboring mobile device.
 21. The apparatus according to claim15, further comprising: means for calculating the location of the mobiledevice at the current time as the following: a weighted sum of thelocation of the mobile device at the current time and the following two;a location obtained by the mobile device at the latest time which iscalculated utilizing the signal received from the satellite; a productof the velocity of the mobile device; and a difference between thecurrent time and the latest time when the mobile device obtained thelocation which is calculated utilizing the signal received from thesatellite.
 22. The apparatus according to claim 14, further comprising:means for determining an actual location calculation interval based thefollowing (i) a shortest location calculation interval, (ii) a totalnumber of a plurality of neighboring mobile devices, (iii) and anadjusting factor, wherein the location calculation interval indicates aninterval between a plurality of times which are calculated utilizingsignals received from the satellite.
 23. The apparatus according toclaim 22, wherein the location message further comprises uniqueidentification of the neighboring mobile device; and wherein determiningthe total number of the plurality of neighboring mobile devicescomprises: sending a plurality of finding messages to the plurality ofneighboring mobile devices; and counting replies from the plurality ofneighboring mobile devices in response to the finding messages as thetotal number of the neighboring mobile devices.
 24. The apparatusaccording to claim 23, further comprising: storing means configured tostore in an association the following: (i) a received location of theneighboring mobile device at the current time, (ii) the current time,(iii) the unique identification of the neighboring mobile device. 25.The apparatus according to claim 22, further comprising means forreceiving a signal from the satellite; and means for calculating thelocation of the mobile device at the current time, in response to achange of the total number of the neighboring mobile devices; and meansfor sending the location of the mobile device at the current time to theof neighboring mobile devices.
 26. The apparatus according to claim 24,further comprising: means for receiving the signal from the satellite;means for calculating the location at a random time between time 0 andthe actual location calculation interval; and means for sending thelocation to the plurality of neighboring mobile devices.